Emphysema is a major cause of death and disability and afflicts approximately 2 million people. The disease cost more than $2.5 billion in annual health care expenses and causes or contributes to the death of 100,000 people each year in the United States alone. The disease is characterized by destruction of the alveolar wall, permanent enlargement of the airspaces and loss of lung recoil capability. Currently approved treatment regimens merely offer symptomatic relief and do not reverse the disease. New effective treatment options are urgently needed, particularly those which reverse the course of disease. Recent studies suggest that hepatocyte growth factor (HGF), a pleiotropic cytokine, has multiple activities that lead to lung regeneration. Such activities include promotion of elastin synthesis, suppression of apoptosis, suppression of inflammation, induction of angiogenesis and stimulation of proliferation of lung epithelial and endothelial cells. HGF production in pulmonary fibroblasts of emphysema patients is known to be impaired. Using gene transfer, HGF has been shown to ameliorate emphysema in animal models, and it can in fact induce a reversal of emphysema in animals with established disease. Thus, experiments with HGF demonstrate the great potential for targeting the HGF signaling pathway for the treatment of emphysema. To overcome the drawbacks of protein- or gene-based HGF delivery in vivo, we have recently developed a small-molecule mimetic of HGF, BB3 (a.k.a. Refanalin). This agent recapitulates the full-range of bioactivities of HGF tested in vitro and in vivo. Refanalin is currently in clinical development for short term intravenous use in kidney transplant patients. It is also being studied as a potential therapeutic in other indications where tissue regeneration is thought to be of critical importance. We have previously found that induction of emphysema by porcine pancreatic elastase (PPE) administration in the rat can be suppressed by co-treatment with BB3. Importantly, we found that daily oral administration of BB3 can reverse established emphysema in the PPE-induced rat model. Additionally, we demonstrated efficacy of BB3 in the TSK1/+ mouse, another model of established emphysema. These results suggest the potential of BB3 as a therapeutic for emphysema with the exciting prospect of reversal of the disease. To further pursue BB3 as emphysema therapeutic, we propose to (1) characterize dose and time dependence of the in vivo efficacy of BB3 in the porcine pancreatic elastase (PPE)-induced rat model of established emphysema, as well as response biomarkers and molecular markers related to protection and regeneration of the lung. (2) Establish the optimal oral dosing regimen for efficacy of BB3 and test the in vivo efficacy of BB3 in the TSK1/+ mouse model and the TGF-(1-induced Balb/c mouse model, two genetically determined models for established emphysema and (3) Test the in vivo efficacy of BB3 in established cigarette smoke-induced emphysema in the mouse. By completing these three specific aims, we will collect important information about the efficacy of BB3 in a breadth of experimental models, in different species and with different genetic backgrounds and molecular stimuli contributing to the establishment of the disease. Furthermore, we'll evaluate molecular markers related to the efficacy of BB3 and to the mechanism of action to stimulate lung regeneration in established emphysema. These data will therefore provide a basis for potential further development of BB3 as a therapeutic for emphysema. PUBLIC HEALTH RELEVANCE: Pulmonary emphysema is a major cause of death and disability that affects approximately 2 million people and costs more than $2.5 billion in annual health care expenses. It directly causes or contributes to the deaths of 100,000 people per year in the United States alone. The disease is characterized by destruction of the alveolar wall, permanent enlargement of the airspaces and loss of lung recoil capability. Currently approved treatment regimens merely offer symptomatic relief and do not reverse the disease. New effective treatment options are urgently needed, particularly those which reverse the disease. Angion Biomedica Corp. has identified BB3, a small molecule mimetic of hepatocyte growth factor (HGF) with excellent drug-like properties. Like HGF, BB3 has the potential to stimulate regenerative processes in the lung and thus reverse established emphysema. With support of an SBIR Phase 1 grant, we have found that daily oral administration of BB3 can indeed reverse established emphysema in the PPE-induced rat model. Additionally, we demonstrated efficacy of BB3 in the TSK1/+ mouse, another model of established emphysema. These promising results show the potential of BB3 as a therapeutic for emphysema with the exciting prospect of reversal of the course of disease. The objective of this phase II SBIR application is to further pursue BB3 as potential emphysema therapeutic. By establishing the exposure levels required for efficacy and by testing efficacy of BB3 in a variety of preclinical models of established disease with different genetic backgrounds and different molecular stimuli contributing to the establishment of the disease, we anticipate to collect important information about the breadth of efficacy of BB3, the oral efficacy in emphysema models and potential response biomarkers. This will provide a basis for potential further development of BB3 as a therapeutic for emphysema.